This application relates to an apparatus and method for identifying the presence of high conductivity or permittivity conditions in a wide range of electrically insulating materials and, more particularly, to a detector to assess the electrical integrity of a polymer insulator.
Insulators are utilized in many applications in the electrical transmission and distribution systems. The main application of an insulator is to mechanically attach current carrying conductors to support grounded structures while electrically insulating the conductors from the grounded structures.
Non-ceramic insulators (“NCI”) (also called polymer or composite insulators) are considered high risk if they contain internal or external defects of conductive or high permittivity. An example of a conductive defect would include internal carbonization of the fiberglass rod due to discharge activity, and an example of a high permittivity defect would be water internal to the insulator.
A requirement for ensuring worker safety when performing live work (“LW”) with polymer insulators is to confirm the short-term (i.e. for the duration of the work) electrical and mechanical integrity of both the installed and the replacement polymer units. Currently there are no generally accepted and easily applied procedures to accomplish this. Consequently, some utilities have opted not to use polymer insulators. In addition, a number of utilities that do use polymer insulators avoid live work on structures on which these insulators have been installed.
A method and apparatus for evaluating nonceramic insulators is described in U.S. Pat. No. 9,063,188 to Phillips et al. the 063' patent describes a device with a V-shaped probe. While effective to evaluate insulators, this type of probe usually requires several sizes of probes to be provided for different sizes of insulators.
Accordingly, there is a need for an apparatus and method that can identify electrical and mechanical integrity of polymer insulators of varying sizes. In addition the sensitivity of the measurement is improved by using a flexible probe that goes all the way around the circular insulator—rather than the two points of contact that a V-shaped probe provides. In addition, there is a need to allow for proves to be placed in the field in the cases that the probes are damaged, or if a different size is needed.